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authorTavian Barnes <tavianator@tavianator.com>2024-10-03 10:52:14 -0400
committerTavian Barnes <tavianator@tavianator.com>2024-10-08 11:46:23 -0400
commitc86dcbc5c0d88d40929c4052a3e866f4a24e1fce (patch)
tree4e336f4942eb07ad94fa701510f43b0bc755e181 /src/trie.c
parent453bf19a9b137a69195ea2cd621910fa02b6e07f (diff)
downloadbfs-c86dcbc5c0d88d40929c4052a3e866f4a24e1fce.tar.xz
trie: Add some extra bounds checking
Diffstat (limited to 'src/trie.c')
-rw-r--r--src/trie.c37
1 files changed, 24 insertions, 13 deletions
diff --git a/src/trie.c b/src/trie.c
index a92950b..ede8811 100644
--- a/src/trie.c
+++ b/src/trie.c
@@ -171,9 +171,10 @@ void trie_init(struct trie *trie) {
}
/** Extract the nibble at a certain offset from a byte sequence. */
-static unsigned char trie_key_nibble(const void *key, size_t offset) {
+static unsigned char trie_key_nibble(const void *key, size_t length, size_t offset) {
const unsigned char *bytes = key;
size_t byte = offset >> 1;
+ bfs_assert(byte < length);
// A branchless version of
// if (offset & 1) {
@@ -185,6 +186,11 @@ static unsigned char trie_key_nibble(const void *key, size_t offset) {
return (bytes[byte] >> shift) & 0xF;
}
+/** Extract the nibble at a certain offset from a leaf. */
+static unsigned char trie_leaf_nibble(const struct trie_leaf *leaf, size_t offset) {
+ return trie_key_nibble(leaf->key, leaf->length, offset);
+}
+
/**
* Finds a leaf in the trie that matches the key at every branch. If the key
* exists in the trie, the representative will match the searched key. But
@@ -206,7 +212,7 @@ static struct trie_leaf *trie_representative(const struct trie *trie, const void
unsigned int index = 0;
if ((offset >> 1) < length) {
- unsigned char nibble = trie_key_nibble(key, offset);
+ unsigned char nibble = trie_key_nibble(key, length, offset);
unsigned int bit = 1U << nibble;
// bits = bitmap & bit ? bitmap & (bit - 1) : 0
unsigned int mask = -!!(node->bitmap & bit);
@@ -307,7 +313,7 @@ static struct trie_leaf *trie_find_prefix_impl(const struct trie *trie, const ch
skip = offset >> 1;
}
- unsigned char nibble = trie_key_nibble(key, offset);
+ unsigned char nibble = trie_key_nibble(key, length, offset);
unsigned int bit = 1U << nibble;
if (node->bitmap & bit) {
unsigned int index = count_ones(node->bitmap & (bit - 1));
@@ -494,10 +500,10 @@ static struct trie_leaf *trie_node_insert(struct trie *trie, uintptr_t *ptr, str
* | Y
* +--->key
*/
-static uintptr_t *trie_jump(struct trie *trie, uintptr_t *ptr, const char *key, size_t *offset) {
+static uintptr_t *trie_jump(struct trie *trie, uintptr_t *ptr, size_t *offset) {
// We only ever need to jump to leaf nodes, since internal nodes are
// guaranteed to be within OFFSET_MAX anyway
- bfs_assert(trie_is_leaf(*ptr));
+ struct trie_leaf *leaf = trie_decode_leaf(*ptr);
struct trie_node *node = trie_node_alloc(trie, 1);
if (!node) {
@@ -507,7 +513,7 @@ static uintptr_t *trie_jump(struct trie *trie, uintptr_t *ptr, const char *key,
*offset += OFFSET_MAX;
node->offset = OFFSET_MAX;
- unsigned char nibble = trie_key_nibble(key, *offset);
+ unsigned char nibble = trie_leaf_nibble(leaf, *offset);
node->bitmap = 1 << nibble;
node->children[0] = *ptr;
@@ -533,8 +539,8 @@ static uintptr_t *trie_jump(struct trie *trie, uintptr_t *ptr, const char *key,
* +--->leaf
*/
static struct trie_leaf *trie_split(struct trie *trie, uintptr_t *ptr, struct trie_leaf *leaf, struct trie_leaf *rep, size_t offset, size_t mismatch) {
- unsigned char key_nibble = trie_key_nibble(leaf->key, mismatch);
- unsigned char rep_nibble = trie_key_nibble(rep->key, mismatch);
+ unsigned char key_nibble = trie_leaf_nibble(leaf, mismatch);
+ unsigned char rep_nibble = trie_leaf_nibble(rep, mismatch);
bfs_assert(key_nibble != rep_nibble);
struct trie_node *node = trie_node_alloc(trie, 2);
@@ -567,8 +573,14 @@ _trie_clones
static struct trie_leaf *trie_insert_mem_impl(struct trie *trie, const void *key, size_t length) {
struct trie_leaf *rep = trie_representative(trie, key, length);
size_t mismatch = trie_mismatch(rep, key, length);
- if (mismatch >= (length << 1)) {
+ size_t misbyte = mismatch / 2;
+ if (misbyte >= length) {
+ bfs_assert(misbyte == length);
return rep;
+ } else if (rep && misbyte >= rep->length) {
+ bfs_bug("trie keys must be prefix-free");
+ errno = EINVAL;
+ return NULL;
}
struct trie_leaf *leaf = trie_leaf_alloc(trie, key, length);
@@ -590,7 +602,7 @@ static struct trie_leaf *trie_insert_mem_impl(struct trie *trie, const void *key
}
offset += node->offset;
- unsigned char nibble = trie_key_nibble(key, offset);
+ unsigned char nibble = trie_leaf_nibble(leaf, offset);
unsigned int bit = 1U << nibble;
if (node->bitmap & bit) {
bfs_assert(offset < mismatch);
@@ -603,7 +615,7 @@ static struct trie_leaf *trie_insert_mem_impl(struct trie *trie, const void *key
}
while (mismatch - offset > OFFSET_MAX) {
- ptr = trie_jump(trie, ptr, key, &offset);
+ ptr = trie_jump(trie, ptr, &offset);
if (!ptr) {
trie_leaf_free(trie, leaf);
return NULL;
@@ -674,9 +686,8 @@ static void trie_remove_impl(struct trie *trie, struct trie_leaf *leaf) {
while (!trie_is_leaf(*child)) {
struct trie_node *node = trie_decode_node(*child);
offset += node->offset;
- bfs_assert((offset >> 1) < leaf->length);
- unsigned char nibble = trie_key_nibble(leaf->key, offset);
+ unsigned char nibble = trie_leaf_nibble(leaf, offset);
unsigned int bit = 1U << nibble;
unsigned int bitmap = node->bitmap;
bfs_assert(bitmap & bit);